The Rama in Y"D 271:7 writes "יש אומרים שיש לכתוב בקולמוס של קנה ולא בנוצה", and the Taz there (s"k 8) says that regarding the kedusha status of printed seforim this process of a metal element applying ink to the paper would be considered kesiva and therefore the seforim would have kedushas seforim and anyone who mistreats these seforim will pay for it later. There is a machlokes between the Aruch Hashulchan (there, s"k 38-39, there he brings a big list of other poskim who hold one way or the other on this issue, ע"ש) and Mishna Berura (32:193) about whether we pasken like this. I know of many rabanim who hold like the Aruch Hashulchan as well as a few who hold like the Mishna Berura. My question (based on the assumption that no one uses old fashion printing presses anymore) is what might be the reason to be machmir for kedushas seforim now? (And I don't think that the Taz would be maskim that lazer printing is also kesiva, עיין his lashon at the very end, ואכמ"ל.)
R" Chaim Kanievsky is machmir on printed seforim nowadays to have 2 coverings in instances that require it (Sefer Ginzei Kodesh P 260;27), while R' Scheinberg and R' Shlomo Zalman are said to have been lenient with just one cover.